Seizo Naemura’s disappearance began with a sudden withdrawal from his former life and persisted for roughly two decades, leaving former pupils and relatives without reliable news of him. When investigators looked for him as a possible link between Hiromi Asai and Michiko Oshitani, his absence became a major investigative lead—but the search also exposed how easily an unexplained disappearance could draw attention away from the truth about another missing man.

Departure and the break with his former life

Naemura’s disappearance can be traced to the end of his career at a junior high school. He quit on March 31, at the close of the academic year, and his divorce followed immediately afterward. He left the apartment he had shared with his wife, without telling her in advance that he intended to leave his job. He left behind a short note and divorce notification; his wife eventually filed her own divorce papers and moved out. The sequence linked the end of his marriage to the end of his employment, although the evidence does not explain what prompted him to abandon both at once.

The departure did not produce a new, traceable address. Naemura did not update the address on his residence certificate after moving out. Local authorities therefore continued sending official mail to the old apartment, even after another person had moved in. When the new resident complained, the authorities canceled Naemura’s registration ex officio. By the time the police investigated, that cancellation had occurred fifteen years earlier, and the administrative record offered no destination to follow.

A disappearance sustained by silence

Naemura’s absence extended beyond official paperwork. His former pupils had no current contact details for him, and Matsumiya concluded that he had not merely disappeared from view but had cut off contact with them. That severance became visible when Michiko Oshitani tried to organize a reunion. She asked a former classmate whether he knew how to reach their old homeroom teacher; he did not, and the reunion plan had to be abandoned because she could not contact Naemura. Another former pupil remembered being asked the same question, confirming that Oshitani had made a genuine effort to find him.

The former pupils still could not say where Naemura had gone. When Matsumiya asked whether they knew of any other older men from their school days whose whereabouts had become unknown, the question widened the inquiry beyond the missing teacher. His disappearance mattered not only because no one could locate him, but because the silence around him left open whether he had chosen to withdraw, been lost to the records, or was connected to someone else’s concealed identity.

The search as an investigative lead

The Tokyo investigators initially focused on Naemura because they needed to identify a missing man who could have been known to both Hiromi Asai and Michiko Oshitani. Shiga Prefectural Police found that he was the only missing person of a suitable age they could identify. With no known family available to explain his later life, Matsumiya and Sakagami were sent to Shiga to pursue the lead. At the orphanage where Hiromi had lived, Matsumiya also asked whether visitor records might show that Naemura had visited her, explaining that former pupils had described him delivering a letter to her in person.

The evidence did not establish that Naemura was the man the investigators sought. Yasuyo Miyamoto’s testimony eventually showed that he was not Shunichi Watabe, the missing person whose connection to Hiromi had become crucial. That distinction forced the task force to reconsider its assumptions: Naemura’s disappearance had pointed toward a possible link, but did not account for Watabe’s relationship with Hiromi or his absence.

What the disappearance concealed—and what it did not explain

Kaga’s re-examination of the case led him to propose that Watabe had been connected to Hiromi for at least ten years and may have received financial support from her. Given Watabe’s age, his disappearance, and his known connection to Michiko, Kaga concluded that he could be Hiromi’s father, Tadao Asai. The novel thus places Naemura’s unexplained withdrawal beside a second, more consequential disappearance: the apparent death of Tadao, which Kaga came to suspect had been fabricated using another person’s death. Naemura’s absence supplied a plausible investigative route, but the resolution depended on separating that route from Watabe’s hidden identity.

Naemura’s story remains defined by what others could not learn: why he left his job and marriage together, where he went, and whether he ever resumed contact with anyone from his earlier life. In the investigation, the missing teacher becomes a measure of the limits of records and recollection. His old pupils remember the failed reunion and the unanswered search, while the authorities can establish a sequence of departures and administrative consequences without recovering the man himself.